The dresses are kind of stretchy, so they will fit a variety of different dolls around Barbie's size. The dresses with the gathers at the bottom will not fit the curvy Barbies. The dresses are rather thin and short. They are form fitting and do not have any Velcro or snaps.
A couple of other dolls clad in black dresses wanted to join the others for the photo below.
The dresses are stretchy enough to fit on my action figure ladies also, however the dresses are so short and tight that I don't recommend that these ladies sit or bend over in these dresses.
I was hesitant at first to try to stretch the little black dresses over my large busted Triad Alpha, so I put her in the dress below, which is a little larger. Later though, I was brave enough to try one of the 6 new dresses on her, and it did fit.